3I/ATLAS (2025)

Orbit of 3I/ATLAS (2025) static (4.8 MB) and animated (31.7 MB).

You Tube video (7/5/25)

Here's a summary of what we know about 3I/ATLAS (C/2025 N1):

• Interstellar Object: It is the third confirmed interstellar object discovered, hence its "3I/" designation. This means it originated from outside our solar system and is currently just passing through.

• Designations:

  • 3I/ATLAS: Its official interstellar object designation.

  • C/2025 N1 (ATLAS): Its official comet designation, indicating it's a non-periodic comet discovered in the first half of July 2025 by the ATLAS survey.

  • A11pl3Z: Its initial, temporary designation.

• Trajectory: It is on a hyperbolic trajectory, confirmed by its negative semi-major axis (A = -0.25996... au). This negative value mathematically signifies an unbound orbit, meaning it will make one pass through our solar system and then escape, never to return. This orbit is also retrograde, meaning that it moves counter to the movement of the planets around the sun. It will pass very close to Jupiter, Mars and Venus, but across the sun from Earth. 

• Perihelion: Its closest approach to the Sun (perihelion) is predicted to be on October 29, 2025, when it will be approximately 1.36 Astronomical Units (AU) from the Sun.

• Discovery Data: The orbital elements and predictions for 3I/ATLAS (July 3, 2025) are based on an observational data arc from June 14, 2025, to July 3, 2025. This short observational period is sufficient for astronomers to calculate its orbit and predict future events like perihelion.

• Ephemeris (JPL Horizons) as of July 3, 2025:

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JPL/HORIZONS                  ATLAS (C/2025 N1)            2025-Jul-04 12:57:37

Rec #:90004916 (+COV) Soln.date: 2025-Jul-03_09:53:57      # obs: 217 (19 days)

 IAU76/J2000 helio. ecliptic osc. elements (au, days, deg., period=Julian yrs):

   EPOCH=  2460857.5 ! 2025-Jul-01.0000000 (TDB)    RMSW= n.a.

   EC= 6.297880223569178   QR= 1.377256245833914   TP= 2460977.6662163921

   OM= 322.3053240978721   W= 127.7776677558638    IN= 175.1184534160558

   A= -.2599636435166625   MA= -173.5472819957557  ADIST= 9.999999E99

   PER= 9.999999E99        N= 7.435927575          ANGMOM= .05453649

   DAN= -3.51672           DDN= 2.06894            L= 194.4267998

   B= 3.8565897            MOID= .38461101         TP= 2025-Oct-29.1662163921

 Comet physical (GM= km^3/s^2; RAD= km):

   GM= n.a.                RAD= n.a.

   M1=  8.7      M2=  n.a.     k1=  10.    k2= n.a.     PHCOF= n.a.

COMET comments 

1: soln ref.= JPL#2, data arc: 2025-06-14 to 2025-07-03

2: k1=10.;

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